Thermometer.



C. SIEBERT.

THERMOMETER.

APPLlCATlON FILED JUNEZZ, 19m.

1 1 99, 1 2 1 Patented Sept. 26, 1916.

By M

I 61 imam oAnL SIEBERT, or CASSEL, GERMANY.

THERMOMETER.

Specification of Letters Patent.

- Application filed June 22, 1914. Serial N o. 846;584.

Toall whom it may concern Be it known that I, CARL SIEBERT, a subject of the German Emperor, and residing at Cassel, Germany, have invented certain new andv useful Improvements in Thermometers, of which the following isa specification.

The present invention has reference to improvements in thermometers, and relates more particularly to a novel construction of thermometer for measuring minute differences of temperature, of the type known as difierential thermometers, and the in-' vention: essentially resides in the particular construction of such athermometer, as will be hereinafter fully described, which in cludes an auxiliary graduated capillary tube communicating respectively with the mercury bulb and the ordinary main capillary" tube, the auxiliary capillary tube being ofpredetermined smaller internal diameter relative to that of the main tube.

With known thermometers of the type re ferred to such improvements are difficult toeifect on account of' its being impossible, owing to the relatively large bore of the thermometer tube, to determine'accurately the quantity of mercury driven through the upper-bent portion of the thermometer'tube into the-receptacle provided at the top of the tube sons to bring the extremity of the mercury thread to adefinite mark within the range of the scale of graduations.

In accordance with the present invention the usual thermometer tube with the ordinary scale for coarse indications, is reduced in bore for some distance adjacent to the mercury bulbwhile separate adjustment and precision scales are provided to facilitatethe performance'of accurate temperature measurements,

In order to make the invention more readily understood, 1 will describe it with reference to the accompanying drawings, in which- Figure 1 represents a front elevation,

partly broken out, of the improved instru* ment, and Fig. 2 a detail part in'section.

The capillary tubeofmy thermometer is composed oftwo communicating parts, of

which the lower part a has a smaller'bore andcommunicates with the mercury-bulb g, and the upper part, with a larger bore 6' communicates with the bent tube reservoir h which is void of air. To the portion blis applied the scale (Z affording ordinary indications of temperatures; temperature of 20 being indicated in the drawing). At the Junct1on c of the two portions of the -thermometer tube, a separating device is fused into the thermometer tube to facilitate detachment of the upper portion of the mercury thread, such device being constituted, for example by a glass pin 7c-asshown in Fig 2-having a microscopically small: orifice i. The lower portion a'of the thermometer tube is equipped with a scale 7 which is the precision scale. The graduati'on marks of thescale are spaced farther apart than the corresponding graduation marks of theupper scale (1 corresponding to the difference in the size of the bores of the respective portions of the-tube, so that-while the: scaled may, for example, he graduated in 1/5 degrees, the scale f may he graduated into- 11/50 degrees or even 1/1000 degrees if the bore of the lower portion (a of the then mom'et'er' tube be made sufiiciently small; A second scale 6 isprovided on the upper tube part, whicli/isupwardly displaced relatively to the first scale cl a distance correspondingto theexact amount of mercury contained in; the 'lower' part of the capillary tube, that is to say frornthelzero point of scale cl downwardly-"to the zero point of the auxiliary= scale for the precision readings.

In the drawing the -graduations are such, that the real1 temperatures are shown by the scale (Z in fifths of a: degree, and the scale f for: precision readings is subdivided in fiftieths of a degree- From zero of. the

rrro.

Patented Sept.26,1916.

scale (1 toi2 there are-ten: parts onthe drawing. As-tl-iis scale' is meant to begraduated into fifths of degrees, the thermometer indicates, if the mercury mountsupwardly to th'e'abov'e mentioned 2; ten fifths of a degree, that is-two degrees The numbers on the scale (Z- and therefore also on the scale 0 mean hereafter whole degrees. As further the scale is meant to be graduatedinto fiftiethsof a degree and the length 0-2 of the scale comprises" 10 parts,. the 2" of this scale means 10 fiftieths OQ". Obviously, by: reducing the diameter of the capillarytube a, the graduations may be brought down" to a as low as tllOHSilllClfillS of degree.

Adjustment of the mercury: thread for out measurements; whereupon the" mercury thread is detached by a jerk in known manner, the separation of the thread being insured by the device provided for the purpose. the mercury thread is allowed to flow into the receptacle h by laying over the instrument where it is temporarily stored. By inclination of the thermometer in the reverse direction the mercury may subsequently be returned from the receptacle h and be reunited with. the thread of mercury.

It will beunderstood that owing to the adjustment .scale 6 being raised relatively to the scale d to the specified extent the extremity of the residual mercury thread will i in all cases fall to the Zero mark of the precision scale f, which constitutes the basis for subsequent precision measurements additive to or subtractive from the first reading afforded by the scale d.

According to the drawing the zero of the scale e, it is true, is by 6 higher than the zero of the scale d. But this is of no importance whatever, as the graduation must by experiment be fixed in such a manner that the contents .of the bore from zero of the scale 6 i to zero of the scale (Z be equal to the contents from zero of the scale (Z (or better from the point 0). to zero of the scale f. If for instance at the beginning of the test the upper or reading end of the mercury stands at zero of the scale d, heat is applied until the reading end stands at zero of the scale 6; if

the instrument is reversed and this stores the Then, heat being applied, the mercury must be driven so high that it shows on the scalee also 183. If now the mercury is detached at the point 0 and the upper part is transferred into the reservoir h, the mercury must fall according tothescale f down to zero, if the temperature sinks down'to its original point, that is to 183. Theoretically spoken it would be desirable to make the detaching-point 0 fall together with zero of the scale d. But this cannot be obtained in manufacturing the thermometer, nor is it necessary, as the precision-measurings are only of a relative nature.

With certain physical researches the chief thing is notto determine the real temperature of each material with accuracy to 1/100 of a degree, but great importance is attached to a relative dilferential precision measurement. Such cases are for example determining the rising of the boiling point or the reduction of the, freezing point, if you Thereupon the detached portion of.

want to determine the molecular weights or calorimetric and similar measurements.-. In thethermometerthe scale cZ shows the real temperature.

point 0, while on the scale f divided into 1/50 degrees, temperature may be read with an accuracy of say hundredths of degrees. The drawing of course is nothing but] aneXample. According to the orifice of the inner. capillary tube the scale (Z might, for instance,- be graduated into tenths and the scale v7" in hundredths, or even in thousan dths, just as theexamination requiresit. If the precision. measurement is to be The scale 6 serves to adjustv the mercury on the scale 7, on which in any made of a temperature lying for instance; above 110 degrees, and 1f youhave only at your (IISPOSELI' the thermometer represented in the drawing, first heat it in order to drive the mercury thread up to forty degreesin the scale d, detach itby tilting the. thermometerat the point a and allow it .to

flow into the receptacle 72,. Repeat then this:

proceeding. Thenheat again until the tern:

perature reaches plus thirty degrees on the scale 6, detach this mercury "thread in :the'

same manner as the-other one and make, it

flow into the reservoirh. There: are now.

altogether 110 (40+4:O+30) detached, and the thermometer; in a temperature of 110 C. registers zero on scale f, whereupon the fine-adjustment is carried out..- For measurements lying just above 0 C. the thermometeris to be adjusted at the zero point of the scale 6. to be cooled in ice until on-the-scale d the degree zero be reached. Then. the thermometer is to be heated until it reaches the zero point on the scale 0, tilted immediately and the mercury is to be run off into the upper reservoir. Then follows th'edesired adjustment for the precision measurement ascending from the zero point of-the scale f; For certain purposes the range of the scale d may extend over 250 C.'. Ad-. jacent to this interval you find, with the necessary space between, the scale. for de-.

tachment. In the same. manner the scale f may he graduated into a more or.lessgreat' number of degrees. Each scale may be sub? divided in microscopical parts of a degree as far as it be technically possible.

The'instrument not alone offers the 'com-,

bined advantages of an absolute and a differential thermometer, butit also. greatly facilitates the adjustment to zero of a differential thermometer.

What I claim is For this purpose it is 1.: A- precision thermometer, comprising a two-part capillary tube and a reservoir, the lower part of said capillary tube having a smaller bore than the upper part and communicating with a mercury bulb and the upper part communicating with said reservoir by a tube bent twice upon itself.

2. A differential thermometer, comprising a two-part capillary tube, a mercury bulb, and a reservoir, the lower tube part communicating with said bulb and being of smaller diameter than the upper tube part, and the latter communicating with said.- reservoir by a tube bent twice upon itself, and a mercury break at the point where the two tube parts meet.

3'. In a differential thermometer, a twopart capillary tube, the lower part being of smaller diameter than the upper part, and a mercury break in the form of a glass member having a microscopically fine longitudinal perforation, said break being located at the meeting place of said two tube parts, and its perforation in co-axial alinement therewith.

4. A difierential thermometer, comprising a two-part capillary tube, the two communicating parts having different diameters, a mercury bulb communicating with the lower tube part of smaller diameter, and a reservoir communicating with the upper tube part of respectively larger diameter by a tube bent twice upon itself and three graduations, one for the real temperature at one side of the upper tube part, another at the other side of the same upper tube part, and one in combination with the lower tube part, the second said graduation being upwardly displaced relatively to the first said graduation a distance corresponding to the amount of mercury between the zero points of the first and third scales.

In testimony whereof I afiix my signature in presence of two Witnesses.

CARL SIEBERT.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner ,of Patents, Washington, D. G. 

